Transmission power control circuit

ABSTRACT

In a transmission power control circuit according to the present invention, a variable gain amplifier ( 1 ) amplifies a transmitting wave with a gain corresponding to a control voltage V C  from a power control section ( 110 ). When a transmission power (P OUT ) of the transmitting wave is within a measurable range of a detecting circuit ( 3 ), the power control section ( 110 ) sets a control voltage feedback ratio (K′) to 0 and applies negative feedback to a detection voltage (V DET ) and thereby, implements close loop control to cause transmission power P OUT  to be closer to a designated level. On the other hand, when the transmission power (P OUT ) is out of a measurable range of the detecting circuit ( 3 ), the power control section ( 110 ) sets a detection voltage feedback ratio (K) to 0 to generate the control voltage (V C ) according to open loop control based on a reference voltage V REF .

TECHNICAL FIELD

[0001] The present invention relates to a transmission power control circuit, and more particularly, to a transmission power control circuit controlling a transmission power of a transmitting wave using a detector.

BACKGROUND ART

[0002] Generally, in a prior art wireless terminal apparatus such as a portable telephone, a feedback control using a detector was performed to control a transmission power of a transmitting wave output.

[0003] Referring to FIG. 24, a transmission power control circuit 10 according to a prior art technique included: a variable gain amplifier 1; a distributor 2; a detecting circuit 3; a reference voltage generating circuit 4; and a power control section 5.

[0004] Variable gain amplifier 1 amplifies a transmission signal with a gain according to a given control voltage V_(C) to generate a transmitting wave output. Distributor 2 takes out part of a transmission power P_(OUT) of a transmitting wave output. Detecting circuit 3 detects part of the transmission power obtained by distributor 2 and generates a detection voltage V_(DET) according to transmission power P_(OUT). That is, detection voltage V_(DET) changes according to transmission power P_(OUT).

[0005] Reference voltage generating circuit 4 generates a reference voltage V_(REF) corresponding to a designated level of transmission power P_(OUT). Power control section 5 generates control voltage V_(C) according to a negative-fed back voltage K₀·V_(DET) obtained by multiplying detection voltage V_(DEF) from detecting circuit 3 by a detection voltage feed-back ratio K₀, and to V_(REF) from reference voltage generating circuit 4, based on the following equation (1).

V _(C) =V _(REF) −K ₀ ·V _(DET)   (1)

[0006] By detecting part of transmission power P_(OUT) of a transmitting wave output using distributor 2 and detecting circuit 3 in such a way to further apply negative-feedback, there can be performed close loop control to cause transmission power P_(OUT) and a designated value P_(CMD) of transmission power to coincide with each other.

[0007] To be concrete, in a case where transmission power P_(OUT) is higher than a designated level, detection voltage V_(DET) becomes higher to, in response to this, lower control voltage V_(C) outputted from power control section 5. As a result, a gain of variable gain amplifier 1 is set small, which works so as to reduce transmission power P_(OUT). To the contrary, in a case where transmission power P_(OUT) is set to a value lower than a designated value, in response control voltage V_(C) is set high, which works so as to raise transmission power P_(OUT) to be large. By performing such a close loop control, control can be executed so that an error between transmission power P_(OUT) of a transmitting wave output and a designated level is reduced to the least possible value.

[0008] Referring to FIG. 25, reference voltage generating circuit 4 includes a transmission power designating section 7; a control section 8; and D/A converter 9. Transmission power designated value P_(CMD) indicating a designated level of a transmission power is converted to reference voltage V_(REF) by control section 8 and D/A converter 9. That is, reference voltage V_(REF) is set in correspondence to transmission power designated value P_(CMD).

[0009] Power control section 5 includes: an operational amplifier 10; and resistance elements 11 and 12. Detection voltage V_(DET) from detecting circuit 3 is transmitted to a node N0 corresponding to the inverted input terminal (−terminal) of operational amplifier 10 through resistance element 12. Reference voltage V_(REF) from D/A converter 9 is inputted to the non-inverting input terminal (+terminal) of operational amplifier 10. Resistance element 11 is coupled between the inverted input terminal and the output terminal of operational amplifier 10. Therefore, detection voltage feed-back ratio K₀ shown in FIG. 28 is determined according to a ratio between resistance elements 11 and 12.

[0010] In such a way, in an architecture of transmission power control circuit 10 according to a prior art technique, it was a precondition that detecting circuit 3 can output a detection voltage corresponding to a transmission power all over a dynamic range of transmission power P_(OUT). However, in a case where a dynamic range of transmission power is set wide, generally, it is rather difficult to broaden a measurable range of detecting circuit 3 than to broaden a dynamic range of a gain of variable gain amplifier 1. With a wider measurable range of detecting circuit 3, a detecting circuit tends to become complex and up-scaled, resulting in a high cost.

DISCLOSURE OF THE INVENTION

[0011] It is an object of the present invention is to provide a transmission power control circuit capable of ensuring a wide dynamic range of transmission power using a general inexpensive detecting circuit having a simple architecture.

[0012] According to the present invention, a transmission power control circuit includes: a variable gain amplifier for amplifying a transmission signal with a gain according to a control voltage to output a transmitting wave; a distributing section for taking out part of the transmitting wave; a detecting section for detecting an output of said distributing section to generate a detection voltage corresponding to a transmission power of the transmitting wave; and a control section receiving an electrical signal indicating a designated level of the transmission power and the detection voltage to set the control voltage. The control section performs a changeover between a first control state setting the control voltage by close loop control according to the detection voltage negative-fed back, multiplied by a feedback ratio and a reference voltage corresponding to the designated level, and a second control state setting the control voltage by open loop control according to the designated level, according to a relationship between a measurable power range of the detecting section and the transmission power.

[0013] The control section preferably performs the changeover between the first and second control states according to the detection voltage.

[0014] Furthermore, the control section preferably performs the changeover between the first and second control states according to a designated level of the transmission power.

[0015] Moreover, the control section preferably includes: a first signal converting section converting a detection voltage to a first digital signal; a control computing section receiving a second digital signal indicating a designated level of a transmission power and the first signal to perform a digital computing for setting a control voltage based on one of the first and second control state, which is selected according to comparison between the first and second digital signals; and a second signal converting section converting an output of the control computing section to an analog signal to generate the control voltage.

[0016] In such a transmission power control circuit, relationships between a designated level of a transmission power and a reference voltage are not set separately inside and outside a measurable range of the detecting circuit but a dynamic range of a transmission power can be widely ensured using a detecting section with a general architecture.

[0017] Furthermore, the control section preferably includes: a feedback ratio adjusting section for gradually reducing a feedback ratio from a prescribed level as a transmission power comes closer to a non-measurable power range in a prescribed boundary range between a measurable power range and non-measurable power range of a detection section in the first control state.

[0018] As a result, a sudden change can be prevented in a transmission power in a prescribed boundary range corresponding to a changeover region between the first control state and second control state.

[0019] The feedback ratio adjusting section more preferably changes a feedback ratio according to a detection voltage.

[0020] The feedback ratio adjusting section more preferably changes a feedback ratio according to a designated level of a transmission power.

[0021] The control section more preferably further includes: a first signal converting section converting a detection voltage to a first digital signal; and a second signal converting section converting an output of the feedback ratio adjusting section to an analog signal to generate a control voltage. The feedback ratio adjusting section receives a second digital signal indicating a designated level of a transmission power and a first digital signal to perform a digital computing for setting a control voltage based on a feedback ratio set according to the second digital signal.

[0022] According to the present invention, the transmission power control circuit includes: a variable gain amplifier amplifying a transmission signal with a gain according to a control voltage to output a transmitting wave; a plurality of distributing sections for taking out part of the transmitting wave; and a plurality of detecting sections, provided corresponding to each of the plurality of distributing sections, respectively, and having different measurable power ranges. The plurality of detecting sections detect outputs of the corresponding distributing sections to generate a plurality of detection voltages according to a transmission power of the transmitting wave. The transmission power control circuit further includes: a control section receiving an electrical signal indicating a designated level of a transmission power and a plurality of detection voltages to set a control voltage. The control section includes: a feedback ratio control section setting a plurality of feedback ratios corresponding to the plurality of detection voltages, respectively, according to a relationship between the measurable power ranges of the plurality of detecting sections and a transmission power. The control section sets a control voltage according to close loop control based on a plurality of detection voltages negative-fed back multiplying each of the plurality of feedback ratios and a reference voltage corresponding to a designated level of a transmission power.

[0023] The measurable power ranges of at least part of the plurality of detecting sections preferably share an overlapped range between any two and the feedback ratio control section, when the transmission power of a transmitting wave corresponds to an overlapped range, sets the feedback ratios so that the detecting voltages from the detecting circuits sharing the overlapped range are synthesized and negative-fed back.

[0024] The feedback ratio control section, when the transmission power of a transmitting wave corresponds to an overlapped region, sets a plurality of feedback ratios so that a synthesis ratio between the plurality of detecting voltages to be synthesized gradually change according to the transmission power.

[0025] Such a transmission power control circuit can implement close loop control with a detective voltage in order to ensure a dynamic range of a transmission power to be wide without increasing a measurable range of each of the plurality of detecting sections, that is by using a plurality of common inexpensive detecting sections. Furthermore, a discontinuous change in transmission power can be prevented in changeover between mainly used detecting circuits according to a relationship between a measurable range of each of the detecting circuits and a detection voltage.

[0026] The feedback ratio adjusting section preferably sets a plurality of feedback ratios according to a plurality of detection voltages.

[0027] Furthermore, the feedback ratio adjusting section preferably sets a plurality of feedback ratios according to a designated level of a transmission power.

[0028] The control section preferably further includes: a first signal converting section for converting a plurality of detection voltages to a plurality of first digital signals; and a second signal converting section converting an output of the feedback ratio adjusting section to an analog signal to generate a control voltage. The feedback ratio adjusting section receives a second digital signal indicating a designated level of a transmission power and a plurality of first digital signals to perform a digital computing for setting a control voltage based on a plurality of feedback ratios set according to a plurality of second digital signals.

[0029] The control section, when a transmission power does not belong to any of the measurable power ranges of a plurality of detecting sections, preferably temporarily ceases close loop control and sets a control voltage based on open loop control corresponding to a designated level of a transmission power.

[0030] Such a transmission control circuit can further control a transmission power based on open loop control of the transmission power at a designated level of transmission power in a range in which the transmission power does not correspond to any of measurable ranges of a plurality of detecting sections. Therefore, a transmission power can be stably controlled without setting relationships between a designated level of a transmission power and a reference voltage separately inside and outside a measurable range of a detecting circuit.

[0031] When an actual transmission power P_(OUT) belongs to one of measurable ranges of detecting circuits, similar to the transmission power control circuit according to the third embodiment, such a transmission power control circuit can implement close loop control with a detective voltage in order to ensure a dynamic range of a transmission power to be wide without increasing a measurable range of each of the plurality of detecting sections, that is by using a plurality of common inexpensive detecting sections. Furthermore, a discontinuous change in transmission power can be prevented in changeover between mainly used detecting circuits according to a relationship between a measurable range of each of the detecting circuits and a detection voltage.

[0032] The control section more preferably performs a changeover between close loop control and open loop control and setting of a plurality of feedback ratios in close loop control according to a plurality of detection voltages.

[0033] The control section more preferably performs a changeover between close loop control and open loop control and setting of a plurality of feedback ratios in close loop control according to a designated level of a transmission power.

[0034] The control section more preferably further includes: a first signal converting section converting a plurality of detection voltages to each of the plurality of first digital signals; and a second signal converting section converting an output of the feedback ratio adjusting section to an analog signal to generate a control voltage. The feedback ratio adjusting section receives a second digital signal indicating a designated level of a transmission power and a plurality of first digital signals to perform a digital computing for setting a control voltage using a plurality of feedback ratios set according to a plurality of second digital signals, based on one of open loop control and close loop control, which is selected according to comparison between first and second digital signals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is a conceptual diagram showing a basic idea of a transmission power control circuit according to the present invention;

[0036]FIG. 2 is a block diagram showing an architecture of a transmission power control circuit according to a first embodiment of the present invention;

[0037]FIG. 3 is a conceptual graph for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 2;

[0038]FIG. 4 is a conceptual graph showing a transmission power control characteristic according to the first embodiment;

[0039]FIG. 5 is a block diagram showing an architecture of a transmission power control circuit according a first modification of the first embodiment of the present invention;

[0040]FIG. 6 is a conceptual graph for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 5;

[0041]FIG. 7 is a block diagram showing an architecture of a transmission power control circuit according a second modification of the first embodiment of the present invention;

[0042]FIG. 8 is a block diagram showing an architecture of a transmission power control circuit according to a second embodiment of the present invention;

[0043]FIG. 9 is a conceptual graph for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 8;

[0044]FIG. 10 is a conceptual graph showing a transmission power control characteristic according to the second embodiment;

[0045]FIG. 11 is a block diagram showing an architecture of a transmission power control circuit according to a first modification of the second embodiment;

[0046]FIG. 12 is a conceptual graph for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 11;

[0047]FIG. 13 is a block diagram showing an architecture of a transmission power control circuit according a second modification of the second embodiment of the present invention;

[0048]FIG. 14 is a block diagram showing an architecture of a transmission power control circuit according to a third embodiment of the present invention;

[0049]FIGS. 15A to 15C are conceptual graphs for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 14;

[0050]FIG. 16 is a block diagram showing an architecture of a transmission power control circuit according a first modification of the third embodiment;

[0051]FIGS. 17A to 17C are conceptual graphs for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 16;

[0052]FIG. 18 is a block diagram showing an architecture of a transmission power control circuit according a second modification of the third embodiment of the present invention;

[0053]FIG. 19 is a block diagram showing an architecture of a transmission power control circuit according to a fourth embodiment of the present invention;

[0054]FIGS. 20A and 20B are conceptual graphs for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 19;

[0055]FIG. 21 is a block diagram showing an architecture of a transmission power control circuit according a first modification of the fourth embodiment;

[0056]FIGS. 22A and 22B are conceptual graphs for describing setting of a detection voltage feedback ratio by a power control section shown in FIG. 21;

[0057]FIG. 23 is a block diagram showing an architecture of a transmission power control circuit according a second modification of the third embodiment of the present invention;

[0058]FIG. 24 is a simplified block diagram showing an architecture of a general transmission power control circuit according to a prior art; and

[0059]FIG. 25 is a diagram for describing a more detailed architecture of the transmission power control circuit according to a prior art shown in FIG. 24.

BEST MODE FOR CARRYING OUT THE INVENTION

[0060] Detailed descriptions will be given of transmission power control circuits according to embodiments of the present invention with reference to the accompanying drawings. Note that the same symbols are attached to the same or corresponding constitutes in the figures and none of descriptions thereof is repeated.

[0061] (First Embodiment)

[0062] Referring to FIG. 1, a transmission power control circuit 100 according to the present invention includes: a variable gain amplifier 1, a distributor 2, a detecting circuit 3; a reference voltage generating circuit 4 and a power control section 110.

[0063] As described in FIG. 24, variable gain amplifier 1 amplifies a transmitting wave with a gain according to a control voltage V_(C) from power control section 110 to generate a transmitting wave output. Distributor 2 takes out part of a transmission power P_(OUT) from the transmitting wave output. Detecting circuit 3 detects the part of a transmission power obtained by distributor 2 to generate a detection voltage V_(DET) corresponding to transmission power P_(OUT). Reference voltage generating circuit 4 generates a reference voltage V_(REF) according to a designated level of transmission power P_(OUT).

[0064] In power control section 110, a detection voltage feedback ratio K and control voltage feedback ratio K′ are set in an interlocked manner according to a relationship between transmission power P_(OUT) and a measurable range of detecting circuit 3.

[0065] Power control section 110 generates a control voltage V_(C) according to the following equation (2) based on reference voltage V_(REF), detection voltage V_(DET) and control voltage V_(C).

V _(C) =V _(REF)−(K·V _(DET) +K′·V _(C))   (2)

[0066] When transmission power P_(OUT) is within a measurable range of detecting circuit 3, close loop control for causing transmission power P_(OUT) to be closer to a designated level can be realized similarly to the equation (1) by setting control voltage feedback ratio K′ to 0 with negative-fed back of detection voltage V_(DET) from detecting circuit 3.

[0067] On the other hand, when transmission power P_(OUT) is outside a measurable range of a detecting circuit 3, detection voltage feedback ratio K is set to 0. As a result of the setting, since a relation that V_(REF)−K′·V_(C)=V_(C) is established, control voltage V_(C) in this case is set as shown in the following equation (3).

V _(C) =V _(REF)/(1+K′)   (3)

[0068] As a result, control voltage V_(C) is generated by open loop control based on reference voltage V_(REF).

[0069] In a transmission power control circuit, a relationship between a transmission power designated value P_(CMD) and reference voltage V_(REF) has been determined on a precondition that negative-feedback through detecting circuit 3 has been performed. Therefore, when transmission power P_(OUT) is outside a measurable range of a detecting circuit 3, transmission power P_(OUT) of a transmitting wave output controlled based on reference voltage V_(REF) produces large error from transmission power designated value P_(CMD) if negative-feedback from detecting circuit 3 is simply cut off.

[0070] In order to avoid this, if negative-feedback from detecting circuit 3 is cut off when transmission power P_(OUT) of a transmitting wave output is outside a measurable range (in a non-measurable range) of detecting circuit 3, control voltage V_(C) is generated using a product of control voltage V_(C) and control voltage feedback ratio K′ as a substitute for the cut-off of the negative-feedback to generate control voltage V_(C). Thereby, it is not necessary to set relationships between transmission power designated value P_(CMD) and reference voltage V_(REF) separately inside and outside a measurable range of detecting circuit 3.

[0071] Referring to FIG. 4, a transmission power control circuit 101 a according to the first embodiment includes: variable gain amplifier 1, distributor 2; detecting circuit 3; reference voltage generating circuit 4 and a power control section 120 a.

[0072] Reference voltage generating circuit 4, similar to the architecture shown in FIG. 25, includes: transmission power designating section 7; control section 8 and D/A converter 9. Transmission power designating section 7 generates transmission power designated value P_(CMD) indicating a designated level of a transmission power. Control section 8 generates a digital signal corresponding to a transmission power designated value P_(CMD) from transmission power designating section 7. D/A converter 9 generates reference voltage V_(REF) having an analog voltage corresponding to a digital signal from control section 8.

[0073] Power control section 120 a includes: a threshold voltage generating circuit 121, a comparator 122, inverter 123, control state changeover switches 124 and 125; an operational amplifier 126; and resistance elements R1 to R3.

[0074] Threshold voltage generating circuit generating a threshold voltage V_(TH) for determining whether or not transmission power P_(OUT) is inside a measurable range of detecting circuit 3 based on detection voltage V_(DET). Comparator 122 compares threshold voltage V_(TH) from threshold voltage generating circuit 121 and detection voltage V_(DET) from detecting circuit 3 with each other.

[0075] To be concrete, when detection voltage V_(DET) is larger than threshold voltage V_(TH), that is when it is determined that transmission power P_(OUT) falls within a measurable range of detection circuit 3, an output of comparator 122 is set at H level. On the other hand, when detection voltage V_(DET) is lower than threshold voltage V_(TH), that is when it is determined that transmission power P_(OUT) falls outside the measurable range of detection circuit 3, an output of comparator 122 is set at L level.

[0076] Reference voltage V_(REF) from D/A converter 9 is inputted to the non-inverting input terminal of operational amplifier 126. Resistance element R1 is coupled between the inverted input terminal and the output terminal of operational amplifier 126. Control voltage V_(C) generated at the output terminal of operational amplifier 126 is transmitted to variable gain amplifier 1.

[0077] Control state changeover switch 124 and resistance element R2 are coupled in series between the inverted input terminal of operational amplifier 126 and detecting circuit 3. Control state changeover switch 125 and resistance element R3 are coupled in series between the inverted input terminal of operational amplifier 126 and ground voltage GND.

[0078] Control state changeover switches 124 and 125 are complementarily turned on/off corresponding to an output of comparator 122. When it is determined that transmission power P_(OUT) falls within a measurable range of detection circuit 3, that is when an output of comparator 122 is set at H level, control state changeover switch 124 is turned on, while control state changeover switch 125 is turned off.

[0079] As a result, detection voltage V_(DEF) as negative-feedback is inputted to operational amplifier 126 through resistance element R2. Therefore, a close loop control system is formed in which control voltage V_(C) is corrected each time according to actual transmission power P_(OUT).

[0080] On the other hand, when it is determined that transmission power P_(OUT) falls outside a measurable range of detection circuit 3, that is when an output of comparator 122 is set at L level, control state changeover switch 125 is turned on, while control state changeover switch 124 is turned off.

[0081] Detection voltage V_(DET) is not transmitted to the inverted input terminal of operational amplifier 126 and operation amplifier 126 operates as a non-inverting amplifier with reference voltage V_(REF) from D/A converter as only one input. Therefore, control voltage V_(C) is generated by an open loop control system only following to reference voltage V_(REF), that is transmission power designated value P_(CMD).

[0082] Referring to FIG. 3, power control section 120 a changes setting of detection voltage feedback ratio K according to a level of detection voltage V_(DET). That is, power control section 120 a, when detection voltage V_(DET) is higher than threshold voltage V_(TH), determines that transmission power P_(OUT) is within a measurable range of detecting circuit 3 to set detection voltage feedback ratio K to K₀. Resistance values of resistance elements R1 and R2 shown in FIG. 2 are designed so as to attain a prescribed feedback ratio K₀.

[0083] On the other hand, power control section 120 a, when detection voltage V_(DET) is lower than threshold voltage V_(TH,) determines that transmission power P_(OUT) is outside a measurable range of detecting circuit 3 to set detection voltage feedback ratio K to 0. That is, negative-feedback of detection voltage V_(DET) is temporarily ceased to perform open loop control. A resistance value of resistance element R3 shown in FIG. 2 is designed in consideration of a relationship between reference voltage V_(REF) and transmission power P_(OUT) in open loop control.

[0084] Referring to FIG. 4, open loop control and close loop control are changed over therebetween based on detection voltage V_(DET) according to transmission power P_(OUT). Within a close loop control range corresponding to inside a measurable range of detecting circuit 3, approximate coincidence occurs between an ideal control response indicated with a dotted line and an actual transmission power indicated with a solid line because of negative-feedback of detection voltage V_(DET).

[0085] On the other hand, within an open loop control range corresponding to outside a measurable range of detecting circuit 3, a gain of variable gain amplifier 1 is set according to transmission power designated value P_(CMD).

[0086] Therefore, no necessity arises for selectively using one of relationships between transmission power designated value P_(CMD) and reference voltage V_(REF) according to an inside/outside measurable range of detecting circuit 3, thereby enabling simplification of an architecture of control section 8.

[0087] As described above, in a transmission power control circuit according to the first embodiment, in a case where, for example, high control precision is required only in a relatively large range of transmission power P_(OUT) but low control precision is allowed in a relatively small range of transmission power P_(OUT), a dynamic range of transmission power can be ensured wide without increasing a measurable range of a detecting circuit, that is using a general inexpensive detecting circuit.

[0088] (First Modification of First Embodiment)

[0089] Referring to FIG. 5, a transmission power control circuit 101 b according to a first modification of the first embodiment is different from transmission power control circuit 101 a shown in FIG. 2 in comparison in that a power control section 120 b is included as constituent instead of power control section 120 a. Power control section 120 b is different from the power control section 120 a shown in FIG. 2 in comparison that threshold voltage generating circuit 121 and comparator 122 is omitted. In power control section 120 b, control section 8 performs issuance of an on/off command of control state changeover switches 124 and 125, that is, a changeover command between open loop control and closed loop control. Control section 8 issues an on/off command for control state changeover switches 124 and 125 according to transmission power designated value P_(CMD).

[0090] Referring to FIG. 6, power control section 120 b, when transmission power designated value P_(CMD) is larger than a prescribed level P_(TH), determines that transmission power P_(OUT) is within a measurable range of detecting circuit 3 to set detection voltage feedback ratio K to K₀. In this case, control state changeover switch 124 is turned on and control state changeover switch 125 is turned off, in response to a command of control section 8.

[0091] On the other hand, power control section 120 b, when transmission power designated value P_(CMD) is lower than a prescribed level P_(TH), determines that transmission power P_(OUT) is out of a measurable range of detecting circuit 3 to set detection voltage feedback ratio K to 0. In this case, control state changeover switch 125 is turned on and control state changeover switch 124 is turned off, in response to a command of control section 8.

[0092] That is, in the first modification of the first embodiment, a determination on whether or not actual transmission power P_(OUT) is within a measurable range of detecting circuit 3 is executed based not on actual detection voltage V_(DET) but on transmission power designated value P_(CMD). Since the other part and operations therein of transmission power control circuit 101 b are similar to transmission power control circuit 101 a shown FIG. 2, none of descriptions thereof is repeated.

[0093] With such an architecture adopted, while a precision in determining whether or not actual transmission power P_(OUT) is within a measurable range of detecting circuit 3 is lowered, a circuit determining a level of detection voltage V_(DET), that is, threshold voltage generating circuit 121 and comparator 122 can be deleted, thereby enabling simplification of an architecture of power control section 120 b.

[0094] (Second Modification of the First Embodiment)

[0095] Referring to FIG. 7, a transmission power control circuit 101 c according to a second modification of the first embodiment is different from the transmission power control circuit 101 a shown in FIG. 2 in comparison in that power control section 120 c is included instead of power control section 120 a. Furthermore, control section 8 and D/A converter 9 are not included and transmission power designated value P_(CMD) from transmission power designating section 7 is given directly to power control section 120 c as a digital signal as is.

[0096] Power control section 120 c includes an A/D converter 135; a control computing section 137; and a D/A converter 139.

[0097] A/D converter 135 converts detection voltage V_(DET) form detecting circuit 3 to a digital signal. Control computing section 137 receives a digital signal according to detection voltage V_(DET) form detecting circuit 3 and transmission power designated value P_(CMD) as a digital signal unchanged to perform a digital computing based on detection voltage feedback ratio K set similarly to FIG. 6. That is, control computing section 137 performs a control operation similar to power control section 110 b constructed as an analog circuit. A result of the operation in control computing section 137 is converted to an analog voltage by D/A converter 139 and transmitted to variable gain amplifier 1 as control voltage V_(C).

[0098] In such a way, in the second modification of the first embodiment, transmission power control similar to the first modification of the first embodiment can be realized by a digital computing.

[0099] Note that, while in the first embodiment and the first and second modifications thereof as well, the architectures are shown in which a design is performed so that a measurable range of detecting circuit 3 corresponds to a relative high range of transmission power P_(OUT), an architecture can be adopted in which a measurable range of detecting circuit 3 corresponds to a relative small range of transmission power P_(OUT) and a correspondence between large/small of transmission power P_(OUT) and setting of open loop control/close loop control is reversed.

[0100] (Second Embodiment)

[0101] In a transmission power control circuit according to the first embodiment, changeover is made between open loop control and close loop control according a result of determination on whether or not actual transmission power P_(OUT) is inside a measurable range of a detecting circuit. As a result of this, since a detection voltage feedback ratio changes stepwise in the vicinity of a changeover boundary region between open loop control and close loop control, there is a risk of a sudden change in transmission power P_(OUT) in the vicinity. Therefore, in the second embodiment, description will be given of a control scheme preventing a sudden change in a transmission power in a changeover boundary region between open loop control and close loop control.

[0102] Referring to FIG. 8, a transmission power control circuit 102 a according to the second embodiment is different from transmission power control circuit 101 a according to the first embodiment shown in FIG. 2 in comparison in that power control section 140 a is included as constituent instead of power control section 120 a.

[0103] Power control section 140 a is different from power control section 120 a shown in FIG. 2 in comparison in that feedback control circuit 142 is incorporated instead of threshold voltage generating circuit 121 and comparator 122; a variable resistor 144 instead of control state changeover switch 124 and resistance element R2; and a variable resistor 146 instead of control state changeover switch 125 and resistance element R3.

[0104] Feedback ratio control circuit 142 controls resistance values of variable resistors 144 and 146 according to detection voltage V_(DET) from detecting circuit 3. Variable resistor 144 is used as means adjusting detection voltage feedback ratio K. Variable resistor 146 is used as means adjusting control voltage feedback ratio K′.

[0105] Referring to FIG. 9, when detection voltage V_(DET) is larger than a prescribed voltage V_(TH2), that is when it is determined that transmission power P_(OUT) is sufficiently within a measurable range of detecting circuit 3, feedback ratio control circuit 142 sets a resistance value of variable resistor 146 to the maximum (∞, ideally). Thereby, detection voltage feedback ratio K is set to K₀ based on a ratio between resistance element R2 and a resistance value of variable resistor 146 to perform close loop control by negative-feedback of detection voltage V_(DET).

[0106] On the other hand, when detection voltage V_(DET) is smaller than a prescribed voltage V_(TH1), that is when it is determined that transmission power P_(OUT) is outside a measurable range of detecting circuit 3, feedback ratio control circuit 142 sets a resistance value of variable resistor 144 to the maximum (∞, ideally). As a result, a non-inverting amplifier with reference voltage V_(REF) as an input is constituted by control voltage feedback ratio K′ according to resistance element R1 and a resistance value of variable resistor 144 to thereby perform open loop control of transmission power P_(OUT) based on transmission power designated value P_(CMD).

[0107] Furthermore, in a region, corresponding to a changeover boundary region between open loop control and close loop control, and in which detection voltage V_(DET) is higher than prescribed voltage V_(TH1) and lower than V_(TH2), feedback ratio control circuit 142 adjusts resistance values of variable resistors 144 and 146 so that detection voltage feedback ratio K gradually changes. In this region, detection voltage feedback ratio K is set so that transmission power P_(OUT) decreases toward outside a measurable range of detecting circuit.

[0108] In comparison of FIG. 10 with FIG. 4, in an architecture according to the second embodiment, there is provided a feedback ratio transition section where detection voltage feedback ratio K gradually changes in a changeover boundary region between open loop control and close loop control to change over between close loop control and open loop; therefore, a sudden change in transmission power can be prevented in the changeover boundary region.

[0109] (First Modification of Second Embodiment)

[0110] Referring to FIG. 11, a transmission power control circuit 102 b according to a first modification of the second embodiment is different from transmission power control circuit 102 a shown in FIG. 8 in comparison in that power control section 140 b is included instead of power control section 140 a.

[0111] Power control section 140 b is different from power control section 140 a shown in FIG. 8 in that feedback ratio control circuit 142 is omitted. In power control section 140 b, resistance values of variable resistors 144 and 146 are controlled by control section 8. Control section 8 sets resistance values of variable resistors 144 and 146 according to transmission power designated value P_(CMD) from transmission power designating section 7.

[0112] Referring to FIG. 12, when transmission power designated value P_(CMD) is larger than prescribed level P_(TH2), that is when it is determined that transmission power P_(OUT) is sufficiently inside a measurable range of detecting circuit 3, control section 8 sets a resistance value of variable resistor 146 to the maximum (∞, ideally). Thereby, detection voltage feedback ratio K is set to K₀ based on a ratio between resistance element R2 and a resistance value of variable resistor 144 to perform close loop control by negative-feedback of detection voltage V_(DET).

[0113] On the other hand, when transmission power designated value P_(CMD) is smaller than prescribed level P_(TH1), that is when it is determined that transmission power P_(OUT) is outside a measurable range of detecting circuit 3, control section 8 set a resistance value of variable resistor 144 to the maximum (∞, ideally). As a result, a non-inverting amplifier with reference voltage V_(REF) as an input is constituted by control voltage feedback ratio K′ according to resistance element R1 and a resistance value of variable resistor 146 to thereby perform open loop control of transmission power P_(OUT) based on transmission power designated value P_(CMD).

[0114] Furthermore, when transmission power designated value P_(CMD) corresponding to a changeover boundary region between open loop control and close loop control is higher than prescribed level P_(TH1) and lower than prescribed level P_(TH2), control section 8 adjusts resistance values of variable resistors 144 and 146 so that detection voltage feedback ratio K gradually changes. Detection voltage feedback ratio K is set similar to the second embodiment so that transmission power P_(OUT) decreases toward outside a measurable range of detecting circuit in a changeover boundary region.

[0115] In such away, in transmission power control circuit 102 b according to the first modification of the second embodiment, whether actual transmission power P_(OUT) is inside or outside a measurable range of detecting circuit 3 is determined not by detection voltage V_(DET) but by transmission power designated value P_(CMD). With such a architecture adopted, while a precision in determining whether or not actual transmission power P_(OUT) is inside or outside a measurable range of detecting circuit 3 is lowered, a circuit (feedback ratio control circuit 142 in FIG. 8) performing determination based on detection voltage V_(DET) is not required any longer in the system; thereby enabling simple architecture of a power control section to be realized.

[0116] While in the second embodiment and the first modification thereof, the architecture is shown in which detection voltage feedback ratio K continuously changes in an changeover boundary region between open loop control and close loop control and an architecture is shown in which variable resistors 144 and 146 each of whose resistance value changes in an analog fashion. As variable resistors, a type whose resistance value gradually changes stepwise may also used. In this case, detection voltage feedback ratio K in a changeover boundary region gradually changes stepwise.

[0117] (Second Modification of Second Embodiment)

[0118] Referring to FIG. 13, transmission power control circuit 102 c according to the second modification of the second embodiment is different from transmission power control circuit 102 a shown in FIG. 8 in comparison in that power control section 140 c is incorporated instead of power control section 140 a. Furthermore, control section 8 and D/A converter 9 are omitted and transmission power designating value P_(CMD) from transmission power designating section 7 is given directly to power control section 140 c as a digital signal as is.

[0119] Power control section 140 c includes: an A/D converter 135; a control computing section 147; and a D/A converter 139.

[0120] Operation in A/D converter 135 is similar to operation described in FIG. 7. Control computing section 147 receives a digital signal corresponding to detection voltage V_(DET) from detecting circuit 3 and transmission power designated value P_(CMD) as a digital signal unchanged to perform a digital computing based on detection voltage feedback ratio K set similarly to FIG. 12. That is, in control computing section 137, a control operation similar to power control section 140 b as an analog circuit. A result of the operation of control computing section 137 is converted to an analog signal by D/A converter 139 and transmitted to variable gain amplifier 1 as control voltage V_(C).

[0121] In such a way, in the second modification of the second embodiment, there can be realized transmission power control similar to the first modification of the second embodiment by a digital computing.

[0122] In the second embodiment and first and second modifications thereof as well, the architectures are shown that is designed so that a measurable range of detecting circuit 3 corresponds to a relative high range of transmission power P_(OUT), an architecture can be adopted in which a measurable range of detecting circuit 3 corresponds to a relative small range of transmission power P_(OUT) and a correspondence between large/small of transmission power P_(OUT) and setting of open loop control/close loop control is reversed.

[0123] (Third Embodiment)

[0124] Referring to FIG. 14, transmission power control circuit 103 a according to the third embodiment is different from transmission power control circuit 101 a according to the first embodiment shown in FIG. 2 in comparison in that there are a plurality of incorporated distributors 2 a, 2 b and 2 c, a first detecting circuit 3 a, a second detecting circuit 3 b and a third detecting circuit 3 c, having respective different measurable ranges. First detecting circuit 3 a, second detecting circuit 3 b and third detecting circuit 3 c are provided corresponding to distributors 2 a, 2 b ad 2 c, respectively.

[0125] First detecting circuit 3 a generates detection voltage V_(DET1) by detecting part of transmission power obtained by distributor 2 a. Second detecting circuit 3 b generates detection voltage V_(DET2) by detecting part of transmission power obtained by distributor 2 b. Third detecting circuit 3 c generates detection voltage V_(DET3) by detecting part of transmission power obtained by distributor 2 c.

[0126] Transmission power control circuit 103 a according to the third embodiment is different from transmission power control circuit 101 a shown in FIG. 2 in comparison in that power control section 150 a is incorporated instead of power control section 120 a.

[0127] Power control section 150 a includes: a feedback ratio control circuit 152; variable resistors 154, 156 and 158; resistance element R2; and an operational amplifier 126.

[0128] Variable resistor 154 is disposed between first detecting circuit 3 a and the non-inverting input terminal of operational amplifier 126 to transmit detection voltage V_(DET1). Variable resistor 156 is disposed between second detecting circuit 3 b and the non-inverting input terminal of operational amplifier 126 to transmit detection voltage V_(DET2). Variable resistor 158 is disposed between third detecting circuit 3 c and the non-inverting input terminal of operational amplifier 126 to transmit detection voltage V_(DET3).

[0129] Feedback ratio control circuit 152 sets resistance values of variable resistor 154, 156 and 158 based on detection voltages V_(DET1), V_(DET2) and V_(DET3).

[0130] Referring to FIGS. 15A to 15C, while first detecting circuit 3 a, second detecting circuit 3 b and third detecting circuit 3 c have respective different measurable ranges, measurable ranges between any two detecting circuits adjacent to each other are set so as to overlap on each other. For example, a measurable range of first detecting circuit 3 a corresponds to a range of V_(DET1)<V_(TH2) and a measurable range of second detecting circuit 3 b corresponds to a range of V_(TH1)<V_(DET2)<V_(TH4). Furthermore, a measurable range of third detecting circuit 3 c corresponds to a range of V_(DET3)>V_(TH3). Established between threshold voltages are relations that V_(TH1)<V_(TH2) and V_(TH4)>V_(TH3).

[0131] Therefore, in a range in which detection voltage is higher than V_(TH1) and lower than V_(TH2), measurement can be performed in both of first detecting circuit 3 a and second detecting circuit 3 b. Similarly, in a range in which detection voltage is higher than V_(TH3) and lower than V_(TH4), measurement can be performed in both of second detecting circuit 3 b and third detecting circuit 3 c

[0132] Feedback ratio control circuit 152 sets resistance values of variable resistors 154, 156 and 158 so that detection voltage feedback ratios K₁, K₂ and K₃ corresponding to respective detection voltages V_(DET1), V_(DET2) and V_(DET3) change as shown in FIGS. 14A to 14C according to a detection voltage.

[0133] Referring to FIG. 15A, when detection voltage V_(DET1) corresponds to a measurable range of first detecting circuit 3 a, that is when V_(DET1)<V_(TH2) feedback ratio K1 corresponding to detection voltage V_(DET1) is set to K₁>0. Especially, when overlapping occurs on a measurable range of second detecting circuit 3 b, that is in a range of V_(TH1)<V_(DET1)<V_(TH2), detection voltage feedback ratio K₁ changes so as to gradually decrease toward a non-measurable range of first detecting circuit 3 a, that is as V_(DET1) approaches V_(TH2). On the other hand, in the other range, that is in a range of V_(TH1)<V_(DET1), detection voltage feedback ratio K₁ is set to prescribed level K₀.

[0134] On the other hand, when detection voltage V_(DET1) corresponds to outside a measurable range of first detecting circuit 3 a (V_(DET1)>V_(TH2,)), detection voltage feedback ratio K₁ is set to 0. In this case, a resistance value of variable resistor 154 is set to the maximum value (∞, ideally).

[0135] Referring to FIG. 15B, feedback ratio K₂ corresponding to detection voltage V_(DET2) is set to K₂>0 when detection voltage V_(DET2) corresponds to a measurable range of second detecting circuit 3 b, that is in a case of V_(TH1)<V_(DET2)<V_(TH4). Especially, in a range where overlapping occurs on a measurable range of first detecting circuit 3 a or second detecting circuit 3 b, that is V_(TH1)<V_(DET2)<V_(TH2) and V_(TH3)<V_(DET2)<V_(TH4), detection voltage feedback ratio K₂ changes so as to gradually decrease toward a non-measurable range of second detecting circuit 3 b. On the other hand, in the other range, that is in a range of V_(TH1)<V_(TH2), detection voltage feedback ratio K₁ is set to prescribed level K₀. Furthermore, still in the other range, that is in a range of V_(TH2)<V_(DET2)<V_(TH3), detection voltage feedback ratio K₂ is set to prescribed level K₀.

[0136] In contrast, when detection voltage V_(DET2) corresponds to outside a measurable range of first detecting circuit 3 b (V_(DET2)<V_(TH1) or V_(DET2)>V_(TH4)), detection voltage feedback ratio K₂ is set to 0. A resistance value of variable resistor 156 is set the maximum value (∞, ideally).

[0137] Referring to FIG. 15C, feedback ratio K₃ corresponding detection voltage V_(DET3) is set to K₃>0, when detection voltage V_(DET3) corresponds to a measurable range of third detecting circuit 3 c , that is in a case of V_(DET3)>V_(TH3). Especially, in a range which overlaps a measurable range of second detecting circuit 3 b, that is in a range of V_(TH)<V_(DET3)<V_(TH4), detection voltage feedback ratio K₃ changes so as to gradually decrease toward a non-measurable range of third detecting circuit 3 c, that is as V_(DET3) comes to closer to V_(TH3). On the other hand, in the other range, that is in a range of V_(DET3)>V_(TH4), detection voltage feedback ratio K₃ is set to prescribed level K₀.

[0138] In contrast, when detection voltage V_(DET3) corresponds to outside a measurable range of third detecting circuit 3 c (V_(DET3)<V_(TH3)), detection voltage feedback ratio K₃ is set to 0. A resistance value of variable resistor 158 is set to the maximum value (∞, ideally).

[0139] With such an architecture adopted, in a range where measurable ranges of first detecting circuit 3 a, second detecting circuit 3 b and third detecting circuit 3 c overlap each other, that is in the vicinity of changeover between mainly used detection circuits, detection voltage feedback ratios K₁ to K₃ are set so that detection voltages from two detecting circuits sharing the overlapped measurable ranges with each other are synthesized and negative-fed back.

[0140] Furthermore, in such a range, detection voltage feedback ratios K₁ to K₃ are set so that a synthetic ratio between synthesized detection voltages gradually changes according to a relationship between a detection voltage and a measurable range of a detecting circuit.

[0141] Therefore, close loop control with a detection voltage for ensuring a wide dynamic range of a transmission power can be implemented without increasing measurable ranges of respective detecting circuits, that is by use of a plurality of general inexpensive detecting circuits. Furthermore, a discontinuous change in transmission power can be prevented in changeover between mainly used detecting circuits according to a relationship between a measurable range of each detecting circuit and a detection voltage.

[0142] (First Modification of Third Embodiment)

[0143] Referring to FIG. 16, transmission power control circuit 103 b according to a first modification of the third embodiment is different from transmission power control circuit 103 a according to of the third embodiment in comparison in that a power control section 150 b is included instead of power control section 150 a.

[0144] Power control section 150 b is different from power control section 150 a shown in FIG. 14 in that feedback ratio control circuit 152 is omitted in architecture. In power control section 150 b, resistance values of variable resistors 154, 156 and 158 are controlled by control section 8. Control section 8 sets resistance values of variable resistors 154, 156 and 158 according to transmission power designated value P_(CMD) from transmission power designating section 7 so that detection voltage feedback ratios K₁, K₂ and K₃ change according to a detection voltage as shown in FIGS. 17A to 17C.

[0145] Referring to FIGS. 17A to 17C, threshold voltages P_(TH1), P_(TH2), P_(TH3) and P_(TH4) are determined correspondingly to measurable ranges of first detecting circuit 3 a, second detecting circuit 3 b and third detecting circuit 3 c, respectively.

[0146] Referring to FIG. 17A, feedback ratio K₁ corresponding to detection voltage V_(DET1) is set to K₁>0 when it is determined that transmission power designated value P_(CMD) corresponds to a measurable range of fist detecting circuit 3 a, that is in a case of P_(CMD)<P_(TH2). Especially, in a range in which overlapping occurs on a measurable range of second detecting circuit 3 b, that is in a range of P_(TH1)<P_(CMD)<P_(TH2), detection voltage feedback ratio K₁ changes so as to gradually decrease toward a non-measurable range of first detecting circuit 3 a, that is as P_(CMD) approaches P_(TH2). On the other hand, in the other range, that is in a range of P_(CMD)<P_(TH1), detection voltage feedback ratio K₁ is set to prescribed level K₀.

[0147] In contrast to this, when it is determined that transmission power designated value P_(CMD) corresponds to outside a measurable range of first detecting circuit 3 a (P_(CMD)>P_(TH2)), detection voltage feedback ratio K₁ is set to 0.

[0148] Referring to FIG. 17B, feedback ratio K₂ corresponding to detection voltage V_(DET2) is set to K₂>0, when it is determined that transmission power designated value P_(CMD) corresponds to a measurable range of second detecting circuit 3 b, that is, in a case of P_(TH1)<P_(CMD)<P_(TH4). Especially, in a range in which overlapping occurs on a measurable range of first detecting circuit 3 a or third detecting circuit 3 c, that is in a range of P_(TH1)<P_(CMD)<P_(TH2) and in a range of P_(TH3)<P_(CMD)<P_(TH4), detection voltage feedback ratio K₂ changes so as to gradually decrease toward a non-measurable range of second detecting circuit 3 b. On the other hand, in the other range, that is in a range of P_(TH2)<P_(CMD)<P_(TH3), detection voltage feedback ratio K₂ is set to prescribed level K₀.

[0149] In contrast to this, when it is determined that transmission power designated value P_(CMD) corresponds to outside a measurable range of first detecting circuit 3 b (P_(CMD)<P_(TH1)or P_(CMD)>P_(TH4)), detection voltage feedback ratio K₂ is set to prescribed level 0.

[0150] Referring to FIG. 17C, feedback ratio K₃ corresponding to detection voltage V_(DET3) is set to K₃>0, when it is determined that transmission power designated value P_(CMD) corresponds to a measurable range of third detecting circuit 3 c, that is, in a case of P_(CMD)>P_(TH3). Especially, in a range in which overlapping occurs on a measurable range of second detecting circuit 3 b, that is in a range of P_(TH3)<P_(CMD)<P_(TH4), detection voltage feedback ratio K₃ changes so as to gradually decrease toward a non-measurable range of third detecting circuit 3 c, that is as P_(CMD) approaches P_(TH3). On the other hand, in the other range, that is in a range of P_(CMD)>P_(TH4), detection voltage feedback ratio K₃ is set to prescribed level K₀.

[0151] In contrast to this, when it is determined that transmission power designated value P_(CMD) corresponds to outside a measurable range of third detecting circuit 3 c (P_(CMD)<P_(TH3)), detection voltage feedback ratio K₃ is set to 0.

[0152] In such a way, in transmission power control circuit 103 b according to the first modification of the second embodiment, it is determined which is a detection circuit corresponding to actual transmission power P_(OUT) according to transmission power designating value P_(CMD). With such an architecture adopted, while determination precision in a detecting circuit having a measurable range corresponding to actual transmission power P_(OUT) is lowered, no necessity arises for a circuit as a constituent (feedback ratio control circuit 152 in FIG. 14) performing a determination based on detection voltages V_(DET1), V_(DET2) and V_(DET3), thereby enabling a simplified circuit architecture for performing transmission power control similar to the second embodiment.

[0153] Furthermore, while in the third embodiment and the first modification thereof as well, the architectures are shown in which variable resistors 154, 156 and 158, respective resistance values changing in an analog fashion, the resistors each may be of a type having a resistance value that changes gradually stepwise.

[0154] (Second Modification of Third Embodiment)

[0155] Referring to FIG. 18, transmission power control circuit 103 c according to a second modification of the third embodiment is different from transmission power control circuit 103 a according to the third embodiment in comparison in that power control section 150 c is included as a constituent instead of power control section 150 a. Furthermore, control section 8 and D/A converter 9 are omitted in the architecture and transmission power designated value P_(CMD) from transmission designating section 7 is given directly to power control section 150 c as a digital signal as is.

[0156] Power control section 150 c has a first A/D converter 135 a; a second A/D converter 135 b; a third A/D converter 135 c; a control computing section 157; and a D/A converter 139.

[0157] First AID converter 135 a; second A/D converter 135 b; and third A/D converter 135 c are provided corresponding to first detecting circuit 3 a, second detecting circuit 3 b and third detecting circuit 3 c, respectively and detection voltages V_(DET1), V_(DET2) and V_(DET3) are converted to digital signals.

[0158] Control computing section 157 receives a plurality of digital signals corresponding to respective detection voltages V_(DET1), V_(DET2) and V_(DET3) and transmission power designated value P_(CMD) as a digital signal unchanged digital to perform a digital computing based on detection voltage feedback ratios K₁, K₂ and K₃, set similarly to FIGS. 17A to 17C. That is, in control computing section 157, there is performed a control operation similar to power control section 150 b. A result of the operation in control computing section 157 is converted to an analog signal by D/A converter 139 and transmitted to variable gain amplifier 1 as control voltage V_(C).

[0159] With such an architecture adopted, in the second modification of the third embodiment, detection voltages V_(DET1), V_(DET2)and V_(DET3) are converted to respective digital signals and close loop control is realized based on a digital computing, thereby enabling realization of transmission power control similar to the first modification of the third embodiment.

[0160] Note that while in the third embodiment and the first and second modifications thereof, the architectures in which there are used the three detecting circuits having respective different measurable ranges, any plural number of such detection circuits can be used. In this case, a necessity rises for providing distributors and variable resistors correspondingly to respective detecting circuits.

[0161] (Fourth Embodiment)

[0162] In the fourth embodiment, description will be given of transmission power control obtained by combining an architecture in which a dynamic range covering a wide range of a transmission power using a plurality of detection circuits which is described in the third embodiment and an architecture in which changeover is made between close loop control and open loop control which is described in the first embodiment.

[0163] Referring to FIG. 19, transmission power control circuit 104 a according to the fourth embodiment is different from transmission power control circuit 101 a according to the first embodiment in comparison in that there is included first detecting circuit 3 a and second detecting circuit 3 b, both having respectively different measurable ranges, and distributors 2 a and 2 b corresponding to first detecting circuit 3 a and second detecting circuit 3 b.

[0164] Furthermore, transmission power control circuit 104 a according to the fourth embodiment includes: power control section 160 a instead of power control section 120 a shown in FIG. 2.

[0165] Referring to FIGS. 20A and 20B, a measurable range of first detecting circuit 3 a corresponds to a range of V_(TH1)<V_(DET1)<V_(TH4) of a detection voltage. On the other hand, a measurable range of second detecting circuit 3 b corresponds to a range of V_(DET2)>V_(TH3) of a detection voltage. Herein, measurable ranges of first detecting circuit 3 a and second detecting circuit 3 b are designed so as to be V_(TH3)<V_(TH4), that is so that parts of measurable ranges are overlapped on each other.

[0166] Referring again to FIG. 19, power control section 160 a includes: operational amplifier 126; resistance element R1; feedback ratio control circuit 162: and variable resistors 164, 166 and 168. Variable resistor 164 is coupled between first detecting circuit 3 a and the inverted input terminal of operational amplifier 126 to transmit detection voltage V_(DET1). Variable resistor 166 is coupled between second detecting circuit 3 b and the inverted input terminal of operational amplifier 126 to transmit detection voltage V_(DET2). Variable resistor 168 is coupled between the inverted input terminal of operational amplifier 126 and ground voltage GND. Resistance element R1 is connected between the inverted input terminal and the output terminal of operational amplifier 126.

[0167] Feedback ratio control circuit 162 set resistance values of variable resistors 164, 166 and 168 based on detection voltages V_(DET1) and V_(DET2).

[0168] Referring again to FIGS. 20A to 20B, in a range in which detection voltages V_(DET1) and V_(DET2) are lower than V_(TH1), detection voltage feedback ratios K₁ and K₂ are both set to 0. That is, in this range, feedback ratio control circuit 162 sets resistance values of variable resistors 164 and 166 to the maximum value (∞, ideally). As a result, a non-inverting amplifier is constituted of operational amplifier 126, resistance element R1 and variable resistor 168, and control voltage V_(C) is set based on open loop control. Resistance element R1 and a resistance value of variable resistor 168 is designed so that prescribed control voltage feedback ratio K′ is obtained.

[0169] In a range in which detection voltages V_(DET1) and V_(DET2) are higher than V_(TH1), a resistance value of variable resistor 168 is set to the maximum value (∞, ideally) to change over from open loop control based on reference voltage V_(REF) to close loop control with negative-feedback of a detection voltage.

[0170] In a range, which corresponds to a region in the vicinity of a changeover boundary region between open loop control and close loop control, and in which a detection voltage is V_(TH1)<V_(DET1)<V_(TH2), a resistance value variable resistor 164 is set so that feedback ratio K₁ gradually increases continuously.

[0171] Furthermore, when detection voltage V_(DET1) is higher than threshold voltage V_(TH2), a resistance value of variable resistor 164 is set so that feedback ratio K₁ is prescribed detection voltage feedback ratio K₀ in a range of V_(TH2)<V_(DET1)<V_(TH3) of a detection voltage. On the other hand, in a range of V_(DET2)<V_(TH3), a resistance value of variable resistor 166 is set to the maximum value (∞, ideally) so that feedback ratio K₂ is 0.

[0172] In a range in which detection voltages V_(DET1) and V_(DET2) are higher than threshold voltage V_(TH3) but lower than V_(TH4), resistance values of variable resistors 164 and 166 are set so that as a detection voltage goes higher, feedback ratio K₁ gradually decreases and in addition, feedback ratio K₂ gradually increases. That is, in a measurable range in which overlapping occurs between a plurality of detecting circuits, a detection voltage feedback ratio is set similarly to the third embodiment. Therefore, in this range, similar to the third embodiment, outputs of a plurality of detecting circuits are synthesized and negative-feedback is implemented. Furthermore, sudden changeover between synthesis ratios does not occur but a synthesis ratio gradually changes.

[0173] With such an architecture adopted, in a range which does not belong to any of measurable ranges of detecting circuits 3 a and 3 b, control voltage V_(C), that is a gain of variable gain amplifier 1, can be set by open loop control based on reference voltage V_(REF), that is transmission power designated value P_(CMD).

[0174] When actual transmission power P_(OUT) corresponds to a measurable range of one of detecting circuits, similar to the transmission power control circuit according to the third embodiment, implementation can be realized of close loop control with a detection voltage for ensuring a wide dynamic range of a transmission power without increasing a measurable range of each detecting circuit, that is by using a plurality of general inexpensive detecting circuits. Furthermore, a sudden change in transmission power in changeover between mainly used detecting circuits can be prevented according to a relationship between a measurable voltage of each detecting circuit and a detection voltage.

[0175] (First Modification of Fourth Embodiment)

[0176] Referring to FIG. 21, transmission power control circuit 104 b according to a first modification of the fourth embodiment is different from transmission power control circuit 104 a shown in FIG. 18 in comparison in that a power control section 160 b is included as constituent instead of power control section 160 a.

[0177] Power control section 160 b is different from power control section 160 a shown in FIG. 19 in that feedback control circuit 162 is omitted as constituent. In power control section 160 b, resistance values of variable resistors 164, 166 and 168 are controlled by control section 8. Control section 8 sets resistance values of variable resistors 164, 166 and 168 according to transmission power designated value P_(CMD) from transmission power designating section 7 so that detection voltage feedback ratios K₁ and K₂ change as shown in FIGS. 20A and 20B according to a detection voltage.

[0178] Referring to FIGS. 22A and 22B, threshold voltages P_(TH1), P_(TH2), P_(TH3) and P_(TH4) are determined correspondingly to measurable ranges of detecting circuits 3 a and 3 b.

[0179] A measurable range of detecting circuit 3 a is determined correspondingly to a range of P_(TH1)<P_(CMD)<P_(TH4) of transmission power designated value P_(CMD). On the other hand, a measurable range of detecting circuit 3 b is determined correspondingly to a range of P_(CMD)>P_(TH3) of transmission power designated value P_(CMD). Overlapped measurable ranges of detecting circuits 3 a and 3 b are determined according to a range of P_(TH3)<P_(CMD)<P_(TH4).

[0180] Control section 8 sets detection voltage feedback ratios K₁ in K₂ not according to a detection voltage but according to transmission power designated value P_(CMD). Setting of detection voltage feedback ratios K₁ and K₂ by control section 8 corresponds to replacement of V_(TH1), V_(TH2), V_(TH3) and V_(TH4) with threshold voltages P_(TH1), P_(TH2), P_(TH3) and P_(TH4).

[0181] Therefore, control section 8, in a range in which transmission power designated value P_(CMD) is lower than P_(TH1), sets detection voltage feedback ratios K₁ and K₂ to 0 and control voltage V_(C) is set only based on open loop control based on reference voltage V_(REF).

[0182] On the other hand, control circuit 8, in a range in which transmission power designated value P_(CMD) is higher than P_(TH1), sets a resistance value of variable resistor 168 to the maximum value (∞, ideally) and changes over from open loop control based on reference voltage V_(REF) to close loop control by negative-feedback of a destruction voltage.

[0183] In a range corresponding to a region in the vicinity of changeover boundary region between open loop control and close loop control, in which transmission power designated value P_(CMD) is P_(TH1)<P_(CMD)<P_(TH2), a resistance value of variable resistor 164 is set so that feedback ratio K₁ gradually increase. In overlapping measurable ranges (P_(TH3)<P_(CMD)<P_(TH4)) between a plurality of detecting circuits, similar to the third embodiment, outputs of a plurality of detection circuits are synthesized and negative-feedback is performed. Moreover, a synthesis ratio gradually changes.

[0184] In such a way, in transmission power control circuit 104 b according to the first modification of the fourth embodiment, which is a detecting circuit corresponding to actual transmission power P_(OUT) is determined according to transmission power designated value P_(CMD). With such an architecture adopted, while reduction occurs in a precision in determination on which one of detecting circuits has a measurable range corresponding to actual transmission power P_(OUT), no necessity arises for a circuit (feedback control circuit 162 shown FIG. 19) performing determination based on destruction voltages V_(DET1) and V_(DET2), enabling simplification of a circuit architecture for implementing transmission power control similar to the second embodiment.

[0185] While in the fourth embodiment and the first modification thereof as well, the architectures are shown in which there are used variable resistors 164, 166 and 168, resistance values all changing in an analog fashion, the variable resistors may be of types whose resistance values change gradually stepwise.

[0186] (Second Example of the Fourth Embodiment)

[0187] Referring to FIG. 23, a transmission power control circuit 104 c according to a second modification of the fourth embodiment is different from transmission power control circuit 104 a according to the fourth embodiment in comparison in that a power control section 160 c is included as constituent instead of power control section 160 a. Furthermore, control section 8 and D/A converter 9 are omitted and transmission power designating value P_(CMD) from transmission power designating section 7 is given directly to power control section 160 c as a digital signal as is.

[0188] Power control section 160 c has a first A/D converter 135 a; a second A/D converter 135 b; a control computing section 167; and a D/A converter 139.

[0189] First A/D converter 135 a and second A/D converter 135 b are provided corresponding to first detecting circuit 3 a and second detecting circuit 3 b, respectively, to convert detection voltages V_(DET1) and V_(DET2) to respective digital signals.

[0190] Control arithmetic logic section 167 receives digital signals corresponding to detection voltages V_(DET1) and V_(DET2) and transmission power designating value P_(CMD) as an digital signal unchanged performs a digital computing based on detection voltage feedback ratios K₁ and K₂ similarly to FIGS. 22A and 22B. That is, in control computing section 167, there are performed a control operation similar to power control section 160 b constructed as an analog circuit. A result of the operation of control computing section 167 is converted to an analog signal by D/A converter 139 and transmitted as control voltage V_(C) to variable gain amplifier 1.

[0191] With such an architecture adopted, in the second modification of the fourth embodiment, detection voltages V_(DET1) and V_(DET2) are converted to respective digital signals and close loop control is realized based on a digital computing, thereby enabling realization of transmission power control similar to the first modification of the fourth embodiment.

[0192] Note that while in the fourth embodiment and the first and second modifications thereof, the architectures are described in which there are included as constituent two detecting circuits having respective different measurable ranges, three or more detecting circuits can also be used. In this case, a pair of a distributor and a variable resistor is required to be provided corresponding to each detection circuit. Similarly, while the example architecture is shown in which the minimum range of a transmission power is changed over to open loop control, a section applied with an open loop can be set corresponding to any power range.

[0193] It should be understood that the embodiments disclosed this time are presented by way of illustration but not to be taken by way of limitation in all aspects. The scope of the present invention is shown not by the above descriptions but the appended claims, and all changes or modifications that falls within bounds of the claims or equivalence of the bounds are intended to be embraced by the claims.

[0194] Industrial Applicability

[0195] A transmission power control circuit according to the present invention can be applied to a wireless communication apparatus such as a portable telephone. 

1. A transmission power control circuit comprising: a variable gain amplifier (1) for amplifying a transmission signal with a gain according to a control voltage (V_(C)) to output a transmitting wave; a distributing section (2) for taking out a part of said transmitting wave; a detecting section (3) for detecting an output of said distributing section to generate a detection voltage (V_(DET)) corresponding to a transmission power (P_(OUT)) of said transmitting wave; and a control section (120 a, 120 b, 120 c, 140 a, 140 b, 140 c) for receiving an electrical signal indicating a designated level (P_(CMD)) of said transmission power and said detection voltage to set said control voltage, wherein said control section performs a changeover between a first control state of setting said control voltage by dose loop control according to the detection voltage negative-fed back by multiplied by a feedback ratio (K) and a reference voltage corresponding to said designated level, and a second control state of setting said control voltage by open loop control according to said designated level, according to a relationship between a measurable power range of said detecting section and said transmission power.
 2. The transmission power control circuit according to claim 1, wherein said control section (120 a, 140 a) performs the changeover between said first and second control states according to said detection voltage (V_(DET)).
 3. The transmission power control circuit according to claim 1, wherein said control section (120 a, 140 a) performs the changeover between said first and second control states according to the designated level P_(CMD)) of said transmission power.
 4. The transmission power control circuit according to claim 1, wherein said control section (120 c, 140) includes: a first signal converting section (135) converting said detection voltage (V_(DET)) to a first digital signal; a control computing section (137, 147) receiving a second digital signal indicating the designated level (P_(CMD)) of said transmission power and said first digital signal to perform a digital computing for setting said control voltage based on one of said first and second control state, which is selected according to comparison between said first and second digital signals; and a second signal converting section (139) converting an output of said control computing section to an analog signal to generate said control voltage (V_(C)).
 5. The transmission power control circuit according to claim 1, wherein said control section (140 a, 140 b, 140 c) includes: a feedback ratio adjusting section (8, 142, 147) for gradually reducing said feedback ratio (K) from a prescribed level (K₀) as said transmission power (P_(OUT)) comes closer to a non-measurable power range in a prescribed boundary range between the measurable power range and said non-measurable power range of said detection section in said first control state.
 6. The transmission power control circuit according to claim 5, wherein said feedback ratio adjusting section (142) changes said feedback ratio (K) according to said detection voltage (V_(DET)).
 7. The transmission power control circuit according to claim 5, wherein said feedback ratio adjusting section (8) changes said feedback ratio (K) according to the designated level (P_(CMD)) of said transmission power.
 8. The transmission power control circuit according to claim 5, wherein said control section (140 c) further includes: a first signal converting section (135) converting said detection voltage (V_(DET)) to a first digital signal; and a second signal converting section (139) converting an output of said feedback ratio adjusting section (147) to an analog signal to generate said control voltage (V_(C)), and said feedback ratio adjusting section (147) receives a second digital signal indicating the designated level (P_(CMD)) of said transmission power and said first digital signal to perform a digital computing for setting said control voltage based on said feedback ratio (K) set according to the second digital signal.
 9. A transmission power control circuit comprising: a variable gain amplifier (1) for amplifying a transmission signal with a gain according to a control voltage (V_(C)) to output a transmitting wave; a plurality of distributing sections (2 a to 2 c) for taking out a part of said transmitting wave; a plurality of detecting sections (3 a to 3 c) provided corresponding to said respective plurality of distributing sections, respectively, and having different measurable power ranges, said plurality of detecting sections detecting outputs of the corresponding distributing sections to generate a plurality of detection voltages (V_(DET1) to V_(DET3)) according to a transmission power (P_(OUT)) of said transmitting wave; and a control section (150 a, 150 b, 150 c, 160 a, 160 b, 160 c) for receiving an electrical signal indicating a designated level (P_(CMD)) of said transmission power and said plurality of detection voltages to set said control voltage, wherein said control section includes a feedback ratio control section (8, 152, 157, 162, 167) setting a plurality of feedback ratios (K₁ to K₃) corresponding to said plurality of detection voltages, respectively, according to a relationship between the measurable power ranges of said plurality of detecting sections and said transmission power, and said control section sets said control voltage according to close loop control based on the plurality of detection voltages negative-fed back multiplying said plurality of feedback ratios, respectively, and a reference voltage (V_(REF)) corresponding to the designated level of said transmission power.
 10. The transmission power control circuit according to claim 9, wherein the measurable power ranges of at least a part of said plurality of detecting sections (3 a to 3 c) share an overlapped range with each other, said feedback ratio control section (8, 152, 157, 162, 167), when the transmission power of said transmitting wave corresponds to said overlapped range, sets said plurality of feedback ratios (K₁ to K₃) so that the detecting voltages from the detecting circuits sharing said overlapped range are synthesized and negative-fed back.
 11. The transmission power control circuit according to claim 10, wherein said feedback ratio control section (8, 152, 157, 162, 167), when the transmission power of said transmitting wave corresponds to said overlapped range, sets said plurality of feedback ratios (K₁ to K₃) so that a synthesis ratio between the plurality of detecting voltages to be synthesized gradually change according to said transmission power.
 12. The transmission power control circuit according to claim 9, wherein said feedback ratio adjusting section (152, 162) sets said plurality of feedback ratios (K₁ to K₃) according to said plurality of detection voltages (V_(DET1) to V_(DET3)).
 13. The transmission power control circuit according to claim 9, wherein said feedback ratio adjusting section (8) sets said plurality of feedback ratios (K₁ to K₃) according to the designated level (P_(CMD)) of said transmission power.
 14. The transmission power control circuit according to claim 9, wherein said control section (150 c) further includes: a first signal converting section (135 a to 135 c) for converting said plurality of detection voltages (V_(DET1) to V_(DET3)) to a plurality of first digital signals; and a second signal converting section (139) converting an output of said feedback ratio adjusting section (157, 167) to an analog signal to generate said control voltage (V_(C)), and said feedback ratio adjusting section (157, 167) receives a second digital signal indicating the designated level (P_(CMD)) of said transmission power and said plurality of first digital signals to perform a digital computing for setting said control voltage based on said plurality of feedback ratios (K₁ to K₃) set according to said plurality of second digital signals.
 15. The transmission power control circuit according to claim 9, wherein said control section (160 a, 160 b, 160 c), when said transmission power does not belong to any of the measurable power ranges of said plurality of detecting sections, ceases said close loop control and sets said control voltage (V_(C)) based on open loop control corresponding to the designated level (P_(CMD)) of said transmission power.
 16. The transmission power control circuit according to claim 15, wherein said control section (160 a) performs a changeover between said close loop control and said open loop control and setting of the plurality of feedback ratios (K₁ to K₃) in said close loop control according to said plurality of detection voltages (V_(DET1) to V_(DET3)).
 17. The transmission power control circuit according to claim 15, wherein said control section (160 b) performs a changeover between said close loop control and said open loop control and setting of the plurality of feedback ratios K₁ to K₃) in said close loop control, according to the designated level (P_(CMD)) of said transmission power.
 18. The transmission power control circuit according to claim 15, wherein said control section (160 c) further includes: a first signal converting section (135 a to 135 c) converting said plurality of detection voltages (V_(DET1) to V_(DET3)) to a plurality of first digital signals, respectively; and a second signal converting section (139) converting an output of said feedback ratio adjusting section (167) to an analog signal to generate said control voltage (V_(C)), and said feedback ratio adjusting section (167) receives a second digital signal indicating the designated level (P_(CMD)) of said transmission power and said plurality of first digital signals to perform a digital computing for setting said control voltage using said plurality of feedback ratios (K₁ to K₃) set according to said plurality of second digital signals, based on one of said open loop control and said close loop control, which is selected according to comparison between said first and second digital signals. 